Secrecy rate maximization in multi-IRS mmWave networks

Abstract

This paper investigates the problem of improving security at the physical layer of a Millimeter Wave (mmWave) network equipped with multiple Intelligent Reflecting Surfaces (IRSs). In this network, the IRSs help the Base Station (BS) in transmitting its signal to the desired user and at the same time improving the physical layer security of the network by preventing the signal to be received by an illegitimate eavesdropper. The target of the proposed scheme is to maximize the secrecy rate by jointly optimizing the active beamforming at the BS and passive beamforming at the IRSs. This is done through a non-convex optimization problem which is solved by decomposing into two sub-problems. The sub-problems are alternatively solved using the Semi-Definite Relaxation (SDR) technique. Finally, simulations are done to assess the performance of the proposed algorithm. These results show the superiority of using multiple IRSs in the enhancement of secrecy rate of the wireless networks in the mmWave frequency bands.